1. Technical Field
The present invention relates to vehicles such as an automobile.
2. Related Art
Known structures of the body of a vehicle such as an automobile include a monocoque structure in which outer plates are welded to a plurality of assembled frame members, and a chassis structure in which frame members are mounted on a chassis base. Safety against collision and favorable running performance are required for the vehicle body, and thus it is generally desired that the vehicle body has high rigidity.
However, multiple performances required for the vehicle body, for example, safety against collision and favorable running performance are not necessarily satisfied at the same time. For example, a front side member, which projects forward from the vehicle compartment and serves as a frame member, supports the engine. In order to achieve favorable running performance, when the vehicle is cornering, the front side member should have high rigidity capable of supporting the engine against the cornering force so as to keep the position of the engine. On the other hand, in order to achieve collision safety performance, the front side member should maintain a relatively high rigidity but absorb a strong impact of a collision by buckling of the front side member. In general, the collision safety performance is given higher priority than the running performance. The running performance is sacrificed for the collision safety performance. For example, the thickness of a sheet metal which is used for a front side member is limited for the sake of the collision safety performance. The length of a front side member is determined according to the size of a vehicle body. Insufficient thickness of the sheet metal of a front side member may cause the front side member to be bent or distorted due to the weight of the engine when the vehicle is cornering. The distortion of the vehicle body affects running performance such as operational responsiveness and steering stability. Such limitation on the rigidity of a vehicle body is applied to not only the front side member. The rigidity of members included in the vehicle body may be limited in order to achieve e.g., the collision safety performance. As a result, for example, as described in Japanese Unexamined Patent Application Publication No. 2005-262951, the vehicle body may be distorted during running of the vehicle even if the vehicle body adopts a structure in which the frame members of the vehicle body are reinforced with a rigid element such as a sheet metal.
As described above, it is desirable to achieve high running performance demanded of the vehicle body, for example, high operational responsiveness and steering stability demanded of sport utility vehicles.